Watching the video today, I want to practice using itnpmRealize cross-domain requests on this machine. First of all, take a look at nodemon.

nodemon

nodemon is used to monitor any changes in the node.js application and automatically restart the service, which is very suitable for use in a development environment.

nodemon will monitor the files in the startup directory, and if any file changes, nodemon will automatically restart the node application.

Nodemon does not require any changes to the code or development methods. Nodemon simply wraps your node application and monitors any files that have changed. nodemon is just a replacement package for node, it just replaces node on the command line when running the script.

nodemon Git address:github.com/remy/nodemon#nodemon

Error summary

First:

nodemon: The "nodemon" item cannot be recognized as the name of a cmdlet, function, script file, or executable program. Please check the spelling of the name, if you include the path
, please make sure the path is correct and try again.
Location line: 1 character: 1
+ nodemon index.js
    + CategoryInfo          : ObjectNotFound: (nodemon:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

the second:

'nodemon' is not an internal or external command, nor an executable program
or batch file。

Using nodemon for the first time:

An error occurred:

nodemon: The "nodemon" item cannot be recognized as the name of a cmdlet, function, script file, or executable program. Please check the spelling of the name, if you include the path
 , Please make sure the path is correct and try again.
 Location Line: 1 Character: 1
+ nodemon index.js
    + CategoryInfo          : ObjectNotFound: (nodemon:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

After checking the Internet, I found out that the nodemon component was not installed. Use the command line:

1. Global installation

npm install -g nodemon

2. Local installation

npm install --save-dev nodemon

After using the global installation, these lines will appear after the installation is complete:

npm WARN optional SKIPPING OPTIONAL DEPENDENCY: [email protected] (node_modules\nodemon\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for [email protected]: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})

+ [email protected]

When testing the code, an error occurred:

nodemon: The "nodemon" item cannot be recognized as the name of a cmdlet, function, script file, or executable program. Please check the spelling of the name, and if you include the path, make sure the path is correct before you    
 Try it once.
 Location Line: 1 Character: 1
+ nodemon index.js
+ ~~~~~~~
    + CategoryInfo          : ObjectNotFound: (nodemon:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

After searching the information online, some netizens said that the results of nodemon and node are the same, but my test results:

At this point, I know that I cannot rely on the solutions on the Internet. So take the way I often use:Overturn and start over

Solution

I chose to enter the project folder in the global cmd:

First install nodemon locally:

npm install --save-dev nodemon

The error that pops up is even more annoying:

'nodemon' is not an internal or external command, nor an executable program
 Or batch file.

Then I reinstalled npm in the project folder, and then reinstalled nodemon

npm install

npm install -g nodemon

Final test

node index.js

Contents of index.js file:

const express = require('express')
const app = express()
const bodyParser = require('body-parser')
// handle static resources
app.use(express.static('public'))
 // Processing parameters
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));

 // Set to allow cross-domain access to the service
app.all('*', function (req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header('Access-Control-Allow-Methods', 'PUT, GET, POST, DELETE, OPTIONS');
  res.header("Access-Control-Allow-Headers", "X-Requested-With");
  res.header('Access-Control-Allow-Headers', 'Content-Type');
  res.header('Access-Control-Allow-Headers', 'mytoken');
  next();
});

 // routing
app.get('/data', (req, res) => {
  res.send('Hello World!')
})

 // start listening
app.listen(3000, () => {
  console.log('running...')
})

Create test.html for testing:

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
         <title>Asynchronous programming ajax</title>
</head>

<body>
    <script src="../js/jquery.min.js"></script>
    <script>
                 /*Traditional jQuery for ajax*/
        var ret = '---';
        $.ajax({
          url: 'http://localhost:3000/data',
          success: function(data) {
            console.log(data)
          }
        });
        console.log(ret)

    </script>
</body>

</html>

Successful output content: